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Nagamatsu, Aiko*; Casolino, M.*; Larsson, O.*; Ito, Tsuyoshi*; Yasuda, Nakahiro*; Kitajo, Keiichi*; Shimada, Ken*; Takeda, Kazuo*; Tsuda, Shuichi; Sato, Tatsuhiko
Physics Procedia, 80, p.25 - 35, 2015/12
Times Cited Count：12 Percentile：95.8(Physics, Applied)JAXA has been investigated the effect of the shielding material for dosimeters in the ISS Russian segment under the ALTCRISS project. The PADLES package is a passive dosimeters which usually consists of two types of passive and integrating dosimeters, a CR-39 plastic nuclear track detector and a thermoluminescence dosimeter. In the ALTCRISS experiments, both tissue-equivalent material CR-39 PNTDs and NAN-JAERI were enclosed in the PADLES packages as radiators for CR-39 to precisely measure a personal exposed doses. We compared the doses obtained by PADLESs with or without the PEs, and with or difference of the two tissue-equivalent materials. The results of space radiation measurements of the ALTCRISS project Phase 1 to 4 using the PADLES system will be reported in this time: Phase 1 experiments was from December 2005 to April 2006, Phase 2 was from April to September 2006, phase 3 was from Sep 2006 to April 2007, and Phase 4 was conducted from May to October 2007.
Kodaira, Satoshi*; Yasuda, Nakahiro*; Hosogane, Tatsuya; Ishikawa, Fumitaka; Kageyama, Tomio; Sato, Mitsuhiro
no journal, ,
The plutonium-thermal use is expected as one of the approach for reuse of spent uranium fuel in nuclear power generation. On the other hand, many kinds of nuclides including Pu with extremely long half-lives are generated in the used fuels, which would be problems for storage and control of radioactive waste. The MOX (Mixed Oxide) consisting of plutonium dioxide enriched with 4-9% Pu and uranium oxide from spent uranium fuel would allow to reduce half-lives of radioactive waste significantly through the nuclear fission. The quality of MOX pellet depends on the homogeneous dispersion of Pu. The region of highly concentrated Pu is sometimes observed as "Pu spot" in the pellet, which has the potential of anomalous combustion localized at that region. The detection of Pu spot and evaluation of its size and concentration are one of the important quality assurance of MOX pellet for the safety use in the nuclear power plant. We have applied CR-39 plastic nuclear track detectors for the measurement of Pu spot inside MOX pellet. CR-39 can image a cross-section of MOX pellet by recording 
-particle tracks from Pu in the pellet, like autoradiography. The Pu spot is visibly imaged as a "black spot" due to the dense tracks compared to homogeneously dispersed region. Conventionally, the Pu spot measurement has been carried out with manual scanning, which takes much longer times and huge amount of human work. We have developed the automatic detection and measurement system of Pu spot recorded on CR-39 by the image processing with filtering and clustering algorithms. The detection efficiency with CR-39 is achieved to be almost 100% compared with conventional manual scanning result. It provides more information about the number, size and position of Pu spot.
Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Faenov, A. Ya.*; Pikuz, T. A.*; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; Matsui, Ryutaro; et al.
no journal, ,
In the laser-driven ion acceleration using cluster-gas target, the acceleration mechanism consists of different processes such as, (a) acceleration of ions due to Coulomb explosion of individual clusters, (b) compression and acceleration of background gas ions due to the Coulomb explosion of clusters, (c) magnetic vortex generation and associated pinching near the rear surface, and (d) sheath acceleration at the interface between the medium and vacuum. To reveal the synergetic interplay between the processes (a) and (b), we have conducted ion acceleration experiments using CO
clusters embedded in background H gas with the J-KAREN laser. By a careful analysis of CR-39, we have found that the maximum energies of protons and carbon ions are 1.5 MeV and 1.1 MeV/u, respectively. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters can be discussed with the help from numerical simulations.
Nishiuchi, Mamiko; Sakaki, Hironao; Nishio, Katsuhisa; Orlandi, R.; Sako, Hiroyuki; Pikuz, T. A.*; Faenov, A. Ya.*; Esirkepov, T. Z.; Pirozhkov, A. S.; Matsukawa, Kenya*; et al.
no journal, ,
The contemporary radiofrequency accelerator technology provides radio-isotope beams for the research. However, the existing technology now faces difficulties in exploring the further frontiers. One of the solutions might be brought by the combination of the state of the art high intensity short pulse laser system and the nuclear measurement technique. Recent progress of the laser technology brought table-top lasers with focused intensity up to 10
Wcm
with only less than 10 J of energy on target. By the interaction with the solid density target, the laser can extract heavy ions in multi-charged state and low emittance, independently on the chemical properties of the target material. We propose Laser-driven Exotic Nuclei extraction-acceleration methods (LENex), in which the exotic nuclei which are the products in the target by the bombardment of the external ion beam, are extracted away by a femtosecond petawatt laser pulse in the form of highly-charged and high energy beam. As a proof-of-experiment of the LENex scheme, we demonstrate the extraction of the almost fully stripped iron ions with the energies of 0.9 GeV by J-KAREN laser system.
